Generally, a printed circuit board is the most elementary part of various electric and electronic products that have been produced to date, and is widely applied to home electric appliances, such as TVs, VTRs, microwave ovens, desktop computers, notebook PCs and the like, and portable electronic products, such as mobile phones, PDAs, MP3s, and the like. Furthermore, with the rapid development of digital electric and electronic instruments and the advancement of semiconductor technology, small-sized, high-density and high-functional printed circuit boards are increasingly used not only for digital satellite products, DVR monitors, palmtop computers, semiconductor modules, digital cameras, semiconductor testing devices, and automotive parts, but also for high-technology weapons in the defense industry, such as missile warheads, fighter planes, satellites, and the like.
Hereinafter, a conventional method of manufacturing a printed circuit board will be described with reference to the attached drawings.
FIGS. 1 to 6 and 7 to 15 are sectional views illustrating methods of manufacturing conventional one-sided, and double-sided or multi-layered printed circuit boards.
First, a method of manufacturing a conventional one-sided printed circuit board will be described with reference to FIGS. 1 to 6.
FIG. 1 shows a Copper Clad Laminate (CCL) including an insulated substrate 11a and a piece of copper foil 11b applied on the insulated substrate 11a. 
Referring to FIG. 2, a dry film 12 including a photosensitizing agent is adhered on the copper foil 11b of the copper clad laminate in order to form a circuit and to be used as an etching resist, and then a circuit 11c is formed through photo exposure and development processes. In addition, the circuit 11c may be formed by circuit-printing and heat-treating (curing) circuit printing ink mixed with a curing agent using a tool referred to as a platemaker.
However, since a circuit formed using circuit printing ink has many electrical and electronic functional problems after part assembly, a process of forming a circuit using a dry film is generally used for quality control.
Referring to FIGS. 3 and 4, the copper foil 11b other than the circuit 11c is etched using the dry film 12, which is developed completely, as an etching resist. Subsequently, an etching resist 12a is removed through a resist stripping process. In this case, a copper chloride solution is chiefly used as an etchant, and a sodium hydroxide solution is chiefly used as a stripping agent.
Referring to FIG. 5, in order to insulate the etched portions of the circuit 11c formed through etching, an insulation layer 13 is formed on the etched portions of the circuit 11c, other than regions in which a surface treatment process will be performed, by performing a commonly-used PSR process (a process of applying an epoxy insulation layer or a polyimide insulation layer on the etched portions of a circuit by printing ink mixed with a photosensitizing agent, heat-treating (partially curing) the printed ink, exposing the heat-treated ink, developing the exposed ink, and then heat-treating (completely curing) the developed ink) or a process of layering a polyimide insulation material thereon.
Referring to FIG. 6, a surface plating layer 14 is formed on the region (SMC PAD or LAND) of the circuit 11c, in which the insulation layer 13 is open, by performing Sn/Pb plating, electroless plating or electrolytic plating in an HSAL (Hot Solder Air Level) process in order to easily perform soldering at the time of part assembly.
Thereafter, a one-sided printed circuit board is completed through post-treatment processes.
Subsequently, a method of manufacturing a conventional double-sided or multi-layered printed circuit board will be described with reference to FIGS. 7 to 15.
FIG. 7 shows a copper clad laminate 21 including an insulated substrate 21a and pieces of copper foil 21b applied on both sides of the insulated substrate 21a. 
Referring to FIG. 8, an electroless copper plating process for forming a copper plating layer 22 on the surface of each of the pieces of copper foil 21b and in the holes of each of the pieces of copper foil 21b is performed such that both of the pieces of copper foil 21b are brought into electrical contact with each other after drilling.
Referring to FIG. 9, a dry film 23 including a photosensitizing agent is adhered closely on each of the copper plating layers 22 of the copper clad laminate 21 in order to form a circuit thereon.
Referring to FIG. 10, after the dry film is completely adhered closely on each of the copper plating layers 22, a resist opening 24, in which a circuit will be formed, is formed by performing photo exposure and development processes.
Referring to FIG. 11, an electrolytic copper plating layer 25 is formed in the resist opening 24, in which a circuit will be formed, and then an electrolytic Sn/Pb plating layer 26 is formed on the electrolytic copper plating layer 25.
Here, the electrolytic copper plating layer 25 is formed to a thickness of 15 to 25 □, and the electrolytic Sn/Pb plating layer 26 is formed to a thickness of 7 to 12 □.
Referring to FIG. 12, the dry film 23, which is an electrolytic copper layer resist, is removed through a stripping process, and then a circuit 29 is formed by etching the exposed copper foil using the electrolytic Sn/Pb plating layer 26 as an etching resist. In this case, an alkali etchant is used as an etchant.
Referring to FIG. 13, the electrolytic Sn/Pb plating layer 26, which is an etching resist, is removed through a stripping process.
Referring to FIG. 14, in order to insulate the etched portions of the circuit 29 formed through etching, an insulation layer 27 is formed on the etched portions of the circuit 29, other than regions in which a surface treatment process will be performed at the time of part assembly, by performing a commonly-used PSR process or a process of layering a polyimide insulation material thereon.
Referring to FIG. 15, a surface plating layer 28 is formed on the region (SMC PAD or LAND) of the circuit 29, in which the insulation layer 27 is open, by performing Sn/Pb plating, electroless plating or electrolytic plating in an HSAL (Hot Solder Air Level) process in order to easily perform soldering at the time of part assembly.
Thereafter, a double-sided or multi-layered printed circuit boards is completed through post-treatment processes.
These conventional methods of manufacturing a printed circuit board have a problem in that connectors are connected by assembling the connectors on an SMC pad of a printed circuit board using soldering at the time of part assembly, thus causing various electrical losses, such as the increase of impedance of the printed circuit board and connectors, the decrease of current efficiency due to electromagnetic wave interference, and the like, and thus the conventional methods are of limited usefulness in the manufacture of small-sized, high-density and high-functional products.